The main branch passes over the Colorado River just south of the Glen Canyon Dam and Lake Powell near Page then enters Utah. The Alternate branch crosses the Colorado River at Navajo Bridge and proceeds to the North Rim of the Grand Canyon before entering Utah.

On February 20, 2013,[5] the main alignment of US 89 was closed in both directions approximately 25 miles (40 km) south of Page due to a landslide that caused the roadway to buckle and subside. Traffic was re-routed via 45 miles (72 km) of secondary and tertiary roads on the Navajo Reservation. Alternate routes through Las Vegas, Nevada, or Hurricane, Utah, and Marble Canyon (US 89A) were also suggested.[6]US 89T (see below) opened in August 2013 as a bypass of the closed section, utilizing Navajo Route 20 as an alignment.

U.S. Route 89T (US 89T) was the designation for Navajo Route 20 (N20), a 44-mile (71 km) road running mostly parallel to U.S. 89 in Arizona. Added to the Arizona state highway system in 2013, US 89T served as a temporary detour for a closed section of US 89.

The need for US 89T arose in February 2013, when a geological event caused a 150-foot (46 m)[7] stretch of US 89 25 miles (40 km) south of Page to buckle. The loss of this stretch of road forced detours for traffic entering the Page area from the south. The Navajo Nation declared a state of emergency.[8] Motorists were rerouted on a 115-mile (185 km) detour via US 160 and SR 98 or a 90-mile detour on N20, which had a 28-mile (45 km) unpaved stretch. At the same time, commute times into Page increased, and merchants in Page and the surrounding area lost significant business.

The Arizona Department of Transportation (ADOT) added the road to the state highway system as US 89T and quickly moved to get money ($35 million from the Federal Highway Administration's emergency relief project fund) and equipment to pave the road. As the Navajo had wanted to pave N20 for decades, and some design and environmental clearances had already been obtained, it took just 79 days to pave N20 in a project that might have otherwise taken more than a year.[9][10] In addition to pavement, right-of-way and fencing to separate the road from the local livestock population were required.[11] The improved road opened to traffic on August 29, 2013. Plans call for the road to be used for three years before the road reverts to Bureau of Indian Affairs jurisdiction.[12]

Initially, the route lacked proper fencing, cattle guards, and pavement markings to support safe travel at higher speeds. As a result, US-89T was open to local traffic only at night, and posted speed limits as low as 25 miles per hour (40 km/h).[9]
As of October 15, US-89T restrictions were lifted following the installation of upgraded control features.[13]

With the reopening of mainline US 89 in March 2015, the US 89T designation was retired and ownership of the route returned to the Navajo Reservation in April 2015.[14]